Dental anchoring device

ABSTRACT

A dental anchoring device ( 8 ) comprises a threaded anchoring pin ( 10 ), connected to a rod ( 13 ) by a weakened waisted portion ( 14 ). Rod ( 13 ) is carried by a main body ( 11 ) with a shaped axial blind bore ( 12 ) for fitting the body onto a drill shank ( 2 ), having a bit ( 5 ) receivable on the bore. The body ( 11 ) has a deformable lip ( 18 ) for snap fitting with a raised ridge ( 6 ) on the shank ( 2 ). A tapered part ( 4 ) of one shank and matching section ( 15 ) of the bore are provided with respective flat faces ( 7, 17 ) to key the shank to the body. Locking groove ( 3 ) keys the shank ( 2 ) into the chuck of a dentists drill. In an alternative embodiment (FIGS.  3  and  4 ), a line of weakness is provided between a metal anchoring pin ( 21 ) and a plastics body ( 27 ), which is severed when a limiting torque is exceeded. allowing the body ( 27 ) to be withdrawn, and the pin ( 21 ) to be left in situ.

TECHNICAL FIELD

[0001] This invention relates to a device for use in dentistry to anchora superstructure to a tooth understructure.

BACKGROUND ART

[0002] It has long been known to insert screws into pre-drilled holes intooth structures to provide anchors for artificial superstructures.Originally this was done with a length of threaded rod which was screwedby hand into a pre-drilled bore using a shaped grip at the end of therod. Surplus projecting rod was then cut off.

[0003] UK patents 1347226 and 1347227 described the use of a threadedrod having a point of weakness between a threaded anchoring part and agripping part. The rod is fully screwed into a pre-drilled bore andfurther screwing action then causes the gripping part to be severed fromthe anchoring part.

[0004] In 1347226 two points of weakness are provided to give differentlengths of anchoring parts, and the gripping part has a shank adapted tofit into a special chuck attachment for a conventional dentist's drill.

[0005] In 1347227, there is one point of weakness, an anchoring head isprovided on the threaded part, and the gripping part has a shank adaptedto fit into a hand tool comprising a knurled knob which can be grippedbetween the fingers.

[0006] UK patent 1482681 describes a threaded rod having an integralshank with a point of weakness therebetween. The shank is shaped to fitdirectly into a conventional dentists drill (i.e. without requiring aspecial chuck or adaptor).

[0007] U.S. Pat. No. 4,202,101 describes one or two part dental anchorswith wings formed on their ends, and a shank with an axial blind bore inwhich the winged end is inserted, the other end of the shank beingadapted for driving connection to a chuck of a dental drill.

[0008] U.S. Pat. No. 4,155,162 describes a two part dental anchor withan L-shaped free end, for engaging in notches in a longitudinal slot ina cylindrical body, giving alternative extensions of the anchor from thebody, as the parts of the anchor are used in turn; U.S. Pat. No.4,053,982 is related to this, disclosing a one, two or three sectioneddental anchor also with an L-shaped free end for engaging in a singlenotch in a cylindrical coupling body.

[0009] GB 1528245 describes a dental hand wrench, with a handling endportion, a cylindrical body, and a threaded pin connected to the body bya wasted portion so that the pin can be separated from the body afterbeing normally screwed into a substrate.

[0010] It is convenient to be able to use the dentists drill to screwthe anchoring device into the tooth. However, the above mentioned priorart arrangements which have this feature, necessitate some modificationor manipulation of the drill. Thus, with the arrangement of GB 1347226it is necessary to fit a special chuck to the drill. With thearrangement of GS 1482681, although a special chuck is not required, itis necessary to remove the drill bit and fit the shank of the anchoringdevice in place of the drill bit.

DISCLOSURE OF INVENTION

[0011] An object of the present invention is to provide an anchoringdevice which can be used with a dentist's drill in a particularlyconvenient manner.

[0012] According to one aspect of the invention therefore there isprovided a dental anchoring device comprising a threaded anchoring part,a connecting part adapted for detachable drivable connection to adentist's drill, and at least one position of weakness between theanchoring part and the connecting part, characterised in that theconnecting part is adapted to be connected to the drill with a drill bitin the drill.

[0013] With this arrangement, conveniently the anchoring device can beconnected to the drill after the drill has been used with a drill bit todrill a bore for the anchoring device in a tooth, without need for thedrill bit to be removed. The threaded anchoring part can then be driveninto the pre-drilled bore using the drill. Once the anchoring part isfully inserted the connecting part can be removed in conventional mannerby severing at the position of weakness caused by further rotation ofthe connecting part by the drill. The severed connecting part can thenbe removed from the drill and discarded leaving the drill bit ready forfurther use.

[0014] With regard to the threaded part this may be a threaded metal rodwhich may be generally of conventional form. The position of weaknessmay be a waisted or cut away portion between the threaded rod and theadjacent portion of the connecting part. The rod, the waisted orcut-away portion and the adjacent portion may be formed in one piece.

[0015] According to a second aspect of the invention, there is provideda dental anchoring device comprising a threaded anchoring part, and aconnecting part adapted for detachable driving connection to a dentist'sdrill, the connecting part being drivably interconnected to theanchoring part so as to be releasable therefrom when a predeterminedlevel of driving torque is exceeded, characterised in that theconnecting part is interconnected with the anchoring part by a structurewhich is adapted to rupture or deform circumferentially to permit saidrelease thereof when said level of driving torque is exceeded.

[0016] Preferably said connecting part is adapted to be connected to thedrill with a drill bit in the drill in accordance with the first aspectof the invention.

[0017] With regard to the rupturable or deformable structure, preferablythis is achieved by drivable interconnection between relatively strongand weak parts, particularly between metal and plastics parts, so thatthe weaker part preferentially ruptures or deforms. Alternatively oradditionally the drivable interconnection may be achieved between partswhich are bonded or welded or similarly fixed together so that the bondor weld or other joint is preferentially ruptured.

[0018] In a particularly preferred embodiment the threaded anchoringpart comprises a rod which is threaded at one end, and the connectingpart comprises a plastics body which is moulded around the other end ofthe rod. The said other end of the rod may be appropriately configured,e.g. by provision of one or more ‘flats’, to drivably key the rodcircumferentially to the plastics body.

[0019] With the first aspect of the invention, and the second aspectwhen combined with the first aspect, the connecting part may have areceptacle in a body thereof to receive the drill bit. This may comprisean axial bore or the like whereby the body is generally of tubularconstruction having solid or open-work side walls. This body may beformed integrally in one piece with the above mentioned adjacent portionor may be a separate part fixed thereto (and may be formed from metal orplastics).

[0020] For detachable drivable connection relative to the drill theconnecting part may incorporate a circumferential locking structurewhich incorporates elements to prevent rotation relative to the drilland/or a longitudinal locking structure which incorporates elements torestrict longitudinal separation from the drill.

[0021] Thus, the connecting part may have side abutment faces or thelike which engage corresponding side abutment faces of the drill bit toprevent relative rotation. Conveniently, the former flat faces may beprovided in the above mentioned axial bore.

[0022] The connecting part may have a deflectable abutment structurewhich makes a releasable snap fit to restrain longitudinal movementrelative to the drill.

[0023] With reference to the connection between the anchoring device andthe drill it is to be understood that this may take place directly, i.e.by interengagement between the anchoring device and the drill chuck, orindirectly i.e. by interengagement between the anchoring device and thedrill bit as more particularly described above. Most preferably thelatter arrangement is adopted and the interengagement is preferablyeffected with a shank part of the drill bit. Whatever drive connectionis adopted this should most preferably be such as to permit readyattachment to give positive drive interconnection, and also to permitready release so that, after use, the device can be conveniently removedto free the drill, and the drill bit for use.

[0024] With regard to the drill, this may be any suitable powereddentist's drill or hand tool; and the bit may be any suitable kind ofdrill bit of twist or other form.

BRIEF DESCRIPTION OF DRAWINGS

[0025] The invention will now be described further by way of exampleonly and with reference to the accompanying drawings in which:

[0026]FIG. 1 is a diagrammatic partially sectional view of one form ofan anchoring device according to the invention mounted on a dentist'sdrill bit;

[0027]FIG. 2 is a cross-section on line II-II of FIG. 1;

[0028]FIG. 3 is a view similar to FIG. 1 of a second form of anchoringdevice according to invention mounted on a dentist's drill bit; and

[0029]FIG. 4 is a cross-section on line IV-IV of FIG. 3.

MODES FOR CARRYING OUT THE INVENTION

[0030]FIGS. 1 and 2 of the drawings show a dentist's drill bit 1 ofgenerally conventional form having a cylindrical shank 2 terminating atone end in a conventional locking structure 3 for engaging the chuck ofa dentist's drill (comprising a part annular groove and a flat face). Atthe other end, the shank 2 has a tapered portion 4 and an axiallyextending twist drill bit 5. The shank 2, tapered portion 4 and drillbit 5 define an integral construction which may be made in one or morepieces.

[0031] There is a slightly raised circumferential ridge 6 between thetapered portion 4 and the shank 2, and the tapered portion 4 has one ormore flat faces 7 thereon (two are illustrated).

[0032] The drawings also show an anchoring device 8 having a connectionpart 9 and an anchoring part 10.

[0033] The connection part 9 has a main body 11 which is of generallycylindrical form with a shaped blind bore 12 extending axially from oneend of the body 11. The other end of the body 11 has an integral rod 13extending axially thereof.

[0034] The rod 13 is formed from metal in one piece with the anchoringpart 10 which is also in the form of a rod. Both rods 10, 13 arecylindrical, the outer surface of the rod 13 being smooth and whollyaxially parallel, and the outer surface of the rod 10 having a regularscrew thread extending throughout its entire length but otherwise havingan axially parallel outer surface. The maximum diameters of the rods 10,13 are identical and between the two rods 10, 13 there is a linkingportion 14 which is waisted or cut away with a circumferential groove todefine a position of weakness.

[0035] The bore 12 in the body 11 is shaped to provide a section 15 atthe open end of the bore 12 tapering inwardly, and a cylindrical section16 extending axially from the small end of the section 15 to the blindend of the bore 12. As shown in the drawings, the bore 12 is shaped tofit snugly over and around the drill bit 5 and the tapered portion 4 andaccordingly, the length and diameter of the section 16 correspond to thedrill bit 5 and the dimensions and shape of the section 15 correspond tothe tapered portion 4 (whereby, as shown, the inner surface of thesection 15 has two flat faces 17 thereto).

[0036] On the inner surfaces of opposite parts of the wider end of thesection 15 there are deformable projections 18 which coact with theraised ridge 6 to form a releasable snap fit.

[0037] Conveniently, the body 11 may be formed from plastics and may bemoulded onto (or firmly push-engaged with) the rod 13.

[0038] With the above arrangement, in use, a tooth stump or the like ispre-drilled with a blind bore using the drill bit 1 fitted in aconventional dentist's drill.

[0039] The anchoring device 8 is then pushed over the drill bit 1 withthe flat faces 17 of the section 15 aligned with the flat faces 7 of thetapered portion 4 until the projections 18 snap-fit over the ridge 6.The anchoring device 8 is thereby held securely in position in that itcannot rotate relative to the bit 1 and it cannot fall longitudinallytherefrom.

[0040] The threaded rod 10 is then screwed into the pre-drilled boreusing the drill (via the drill bit 1). When the rod 10 is fully insertedthe anchoring device 8 severs at the position of weakness 14 leaving thethreaded rod 10 fixed securely in the tooth and projecting therefrom.The remaining part of the anchoring device (i.e. the connecting part 9comprising the body 11 and the rod 13) can then be pulled off the bit 1and discarded. The bit 1 can then be used as required.

[0041] With this arrangement the inconvenience of having to remove thebit 1 to use the drill to insert an anchoring device 8 is avoided.

[0042] As shown in FIGS. 3 and 4, a second embodiment of dentalanchoring device comprises a metal rod 21 which is threaded at one end22.

[0043] At its opposite end 23 the rod 21 is shaped, e.g. with ‘barb’structures 24, to provide an anchoring part for anchoring a toothsuperstructure. At the tip of this end of the rod there is an enlargedhead 25 with a flat 26 on one side.

[0044] A connecting part 27 in the form of a plastics body (ofthermoplastics material) is injection moulded around the end 23 of therod 21. The body 27 is generally cylindrical (or frusto-conical). It isaxially aligned with the rod 21 and has a blind bore 28 which tapersinwardly over part of its length from its open end or receptacleextending axially from the end remote from the rod 21. The body 27 issecured to the rod 21 by the adhesion arising from the injectionmoulding process and also by the interlocking effect of the enlargedhead 25 with the flat 26 and the barbs 24.

[0045] In use the anchoring device is attached to a drill bit 29 asshown in FIG. 3 and the threaded end 22 is drilled into a pre-drilledbore in a tooth stump.

[0046] When the end 22 is fully inserted the rod 21 automaticallyseparates from the plastics body 27. This arises because the increase intorque causes the plastics material to deform or rupture at itsinterface with the rod 21 so that there is relative movement between therod 1 and the plastics body 27 giving rise to the formation of theloose-fitting bore. The plastics body 27 then readily separates from therod 21. This interface thus comprises a position of weakness inaccordance with the present invention. If desired it is also possible tohave a further point of weakness in the rod 21.

[0047] It is of course to be appreciated that the invention is notintended to be restricted to the details of the above embodiment whichare described by way of example only. Thus, for example, in the firstembodiment, the diameters of the rods 10, 13 need not be the same. Theend of the rod 10 adjacent the position of weakness 14 may have anenlargement if desired. There may be two or more positions of weakness14. The shapes of the sections 15, 16 and the projections 18 may bedifferent as desired and in accordance with the shape of the bit 1.

1. A dental anchoring device comprising a threaded anchoring part, a connecting part adapted for detachable drivable connection to a dentist's drill, and at least one position of weakness between the anchoring part and the connecting part characterised in that the anchoring part is adapted to be connected to the drill with a drill bit in the drill.
 2. A dental anchoring device according to claim 1 wherein the position of weakness is a waisted portion, or a cut-away portion, between the threaded rod and the adjacent portion of the connecting part.
 3. A dental anchoring device according to claim 2 wherein the rod, the waisted or cut away portion and the adjacent portion are formed in one piece.
 4. A dental anchoring device according to claim 1 wherein the position of weakness is a structure which is adapted to rupture or deform circumferentially to permit release of the threaded part when a level of driving torque is exceeded.
 5. A dental anchoring device according to claim 1, 2, 3 or 4 wherein the connecting part has a receptacle in a body thereof to receive the drill bit comprising an axial bore whereby the body is generally of tubular construction.
 6. A dental anchoring device according to claim 5 wherein for detachable drive connection relative to the drill, the connecting part incorporates a circumferential locking structure which incorporates elements to prevent rotation relative to the drill.
 7. A dental anchoring device according to any preceding claim wherein the connecting part has side abutment faces which engage corresponding side abutment faces of the drill bit to prevent rotation.
 8. A dental anchoring device according to claim 7, wherein the connecting part has a deflectable abutment structure which makes a releasable snap fit to restrain longitudinal movement relative to the drill.
 9. A dental anchoring device comprising a threaded anchoring part, and a connecting part adapted for detachable driving connection to a dentist's drill, the connecting part being drivably interconnected to one anchoring part so as to be releasable therefrom, when a predetermined level of driving torque is exceeded, characterised in that the connecting part is interconnected with the anchoring part by a structure which is adapted to rupture or deform circumferentially to permit said release thereof when said level of driving torque is exceeded.
 10. A dental anchoring device according to claim 4 or claim 9, wherein the rupturable or deformable structure is achieved by drivable interconnection between relatively strong and weak parts, so that the weaker part preferentially ruptures or deforms.
 11. A dental anchoring device according to claim 4 or claim 9, wherein the rupturable or deformable structure is achieved by drivable interconnection between parts which are bonded or welded or similarly fixed together so that the bond or weld or other joint is preferentially ruptured.
 12. A dental anchoring device according to claim 10 wherein the threaded anchoring part comprises a metal rod which is threaded at one end, and the connecting part comprises a plastics body which is moulded around the other end of the rod, said other end of the rod being appropriately configured to drivably key the rod circumferentially to the plastics body. 